As cheesemaking has developed over the years it has become an activity accomplished in larger and larger processing plants, which benefit from efficiencies of scale. As a result, it has become more cost effective for the owners of these plants to process the by-products of cheesemaking. In particular, whey has been shown to have value to cheesemakers due to the value of non-casein proteins, which remain in whey after cheesemaking. These proteins are generally recovered as whey protein concentrates (WPC) or whey protein isolates (WPI) through further processing of the whey. Whey protein concentrates and isolates are typically produced through a series of process steps, which typically include ultrafiltration, evaporation, and drying. A significant demand for such products has developed in the food industry.
Secondary products of this recovery process include a fluid generally referred to as “permeate.” The term permeate is generally used to refer to a HLAF which passes through, or permeates through, membrane filters used in ultrafiltration of whey. Typically, about 15% to 30% of the total solids in whey are recovered as the whey protein concentrate/whey protein isolate (WPC/WPI) during traditional ultrafiltration or any of the other known processes for isolating whey proteins. Permeate, therefore, generally contains about 70 to about 85% of the total solids in the whey. These figures vary depending upon the process used to generate the WPC/WPI, but it will be appreciated that, in each case, a larger percentage of the solids is recovered with the permeate than is recovered with the protein fraction isolated as WPC/WPI.
Permeate is an aqueous fluid predominantly containing lactose, along with some low molecular weight proteins, non-protein nitrogen components, minerals, vitamins, and other constituents. The removal of casein and non-casein proteins from milk, however, generally makes the remaining solids in permeate more difficult to dry than might be the case if these proteins were retained in the aqueous fluid. Such proteins are generally considered to be a “drying aid”. Since virtually all of the casein and the majority of the non-casein proteins have been removed at this stage of milk processing, permeate is difficult to dry in a cost effective manner. It is this challenge that is addressed by the present invention.
In commercial operations, permeate is often concentrated by a series of steps including reverse osmosis and/or evaporation, which take the fluid to a total solids concentration of about 60%. This concentrated fluid is then crystallized and centrifuged to separate a portion of the lactose that can be further refined, dried, and sold as a commodity product. The remaining “delactosed permeate” (DLP) is generally viewed as a zero-value by-product, even though it generally contains from about 30 to about 35% of the original whey solids from which first the whey protein concentrate/isolate and then the lactose were isolated. The DLP is generally used as a feed supplement for animals. The cost of shipping DLP is generally about the same as its value for animal feed, which is why it is generally considered to be a zero-value by-product.
In the past, many processing plants regarded DLP as a waste product and disposed of it as best they could. Today, with the increase in size of cheese plants and with the general increase in environmental regulations, waste disposal of DLP is not a viable option. If further value could be drawn from the DLP through more cost-effective processing, however, it is believed that the cheese processing industry would embrace such improved processing techniques.
It will be appreciated that the value of the lactose and other milk constituents remaining in the DLP would have value only if they could be recovered in a form that can be used for purposes other than a low-value, liquid feed supplement. The challenge the industry has faced has been that none of the processes presently available to the industry provide an efficient way to recover all of the lactose and other milk constituents remaining in the DLP in a form conducive to marketing these constituents as food ingredients or high-value feed products.
It will be appreciated that there is significant value in dried, high-lactose products; therefore, a new process that can better enable the dairy industry to produce useful high-lactose products from permeates and other HLAFs and new systems for utilizing this process will provide a desired advance over the prior art methods and systems for isolating lactose and other milk constituents from HLAFs.